The present invention relates generally to water treatment system (WTS) units, and more particularly, to WTS units which employ light sensors to determine when the WTS units are filtering and sterilizing water properly.
Water treatment system (WTS) units often employ filters to remove particulates and employ reactors containing ultraviolet (UV) lamps to destroy microorganisms in water being treated. Filters are generally replaced when either the filters have treated a predetermined quantity of water or when the filters have been in a WTS unit for a predetermined length of time. Even if only a small amount of water has been filtered, microorganism growth over time in the filter makes filter replacement desirable.
Similarly, UV lamps or bulbs also must be replaced. As time passes, the light intensity from light sources, such as UV bulbs, diminishes resulting in water passing through a light reactor vessel receiving diminishing amounts of UV light dosage. Sensors are often used to directly sense the UV light intensity coming from the UV bulb. When the sensors determine that the intensity has decreased below a threshold value, a signal is often given off by the WTS unit advising a user that the UV bulb should be replaced.
Conventional light sensing systems have several shortcomings. First, it is possible that water of increased turbidity or dirtiness may accidentally reach the UV reactor. In such a case, the increased turbidity may prevent all the water passing through the reactor from receiving the minimally desired quantity of UV light dosage even though the UV bulb is emitting a sufficient intensity of light. Second, as the intensity of the UV bulb diminishes over time, the water may or may not receive a minimum desired dosage of UV light due to fluctuations in turbidity. If the water is quite clear, then microorganisms residing in the water will receive a sufficient dosage of UV light even if the intensity of the UV light has decreased. However, if increased particle turbidity exists, then under otherwise satisfactory UV light intensity output from the UV bulb, some microorganisms shaded by the turbidity may not receive the desired dosage.
Water treatment standards include a NSF standard 55 Class A. Standard 55 Class A requires that light intensity be sensed after passing through water which is being treated. This accommodates the changing turbidity in the water. However, to date, few if any WTS units meet this standard 55.
The present invention is intended to provide a method and apparatus for addressing these shortcomings.
The present invention includes an apparatus and method for filtering and sterilizing water using a turbidity and microorganism sensing system in a WTS. The sensing system includes a UV light source, a flow path through which water to be treated with UV light passes, and at least one light sensor which receives UV light having passed through the flow path. The light sensor includes a light pipe and a visible light detector which may be a photocell. The light sensor contains a fluorescent dye which causes UV light striking the light pipe to fluoresce and emit visible light. The visible light is sensed by the photocell. The light sensor is in communication with a microprocessor for processing the intensity of the UV light sensed by the light sensor, converting the sensed visible light intensity to a UV light intensity, and comparing the UV light intensity against a UV light intensity standard. Another aspect of the invention includes a light sensor located proximate to the UV light source to receive direct UV light intensity. This UV light sensor can be used as a UV light intensity standard. Another aspect of the invention includes a light sensor having no fluorescing action and, thus, only sensing visible light to determine turbidity levels. Another aspect of the invention includes an alarm for signaling that the difference in the sensed and standard UV light intensities is sufficiently large that the system is not functioning properly. The sounding of the alarm could represent either turbidity and/or a high amount of microbiologicals in the water. In yet another aspect of the invention, the system includes at least one valve which reacts to the difference between the UV light intensity standard and the sensed UV light intensity and adjusts the volume of water flowing through the WTS such that the amount of turbidity and microorganisms flowing through the system is regulated to a manageable level. The valve controls the contact time of the UV light through the water by regulating water flow and the UV dose delivered to the water.